Chapter 12, Problem 44A

Summary Introduction

To explain:

The possible copying mechanism in DNA as per the description given by Person W and Person C.

Introduction:

Person W and Person C built a model of the double helix for DNA that conformed to other scientists’ research. Together they solved the structure of DNA. They suggested that DNA was a double helix formed by two strands of nucleotides twisted around each other.

Answer to Problem 44A

The specific base pairing explains the copying mechanism in DNA.

Explanation of Solution

According to Person W and Person C’s model of DNA, there are two chains of nucleotides that are held together by the nitrogenous bases. The bases are joined together by weak hydrogen bonds. They form pairs with one purine base from one chain hydrogen bonded to a single pyrimidine base from the other chain. Adenine and guanine are purines while thymine and cytosine are pyrimidine bases.

The hydrogen bonds can form only between specific bases, so the bases on one strand determine the bases on the other strand. So adenine on one strand will pair with only thymine on the other strand, and guanine will pair with cytosine. These base pairs are called complementary base pairs. This specific base pairing is responsible for the copying mechanism in DNA. During replication each new strand formed is complementary to the original strand due to specific base pairing mechanism.